1. Field of the Invention
This invention relates to the general field of information storage and more particularly to a storage system for video data that is simultaneously accessible by multiple client stations.
2. Background
Magnetic disks have largely supplanted video tape as the storage medium of choice for many video production tasks. In many cases, it is desirable to have the capability for multiple production resources to simultaneously access a central video storage device. For example, consider the commercial insertion task of a local broadcast televisions station. A television program is received from a network feed or is played from a video tape. At appropriate times, the television station must insert commercial messages or other spot announcements. Before the advent of disk storage, each commercial would be recorded on a separate video tape cassette. Prior to a commercial break, the appropriate cassettes would be loaded into a bank of cassette players which would then be cued at the proper times by an editor or automatic player control system.
A disk-based video storage system permits the broadcast station to store all of the commercials and other spot insertions for random access. The appropriate sequence of commercials and other spots can then be easily retrieved for insertion during breaks in the broadcast program. It is desirable to have access to the disk-based video storage by various workstations and other components in the broadcast station. In order to provide such access capabilities, it has heretofore been necessary to couple the disk storage unit or units to a network file server. The server is typically a relatively expensive piece of hardware and creates a bottleneck for access to the stored video data. Individual client stations attempting to access video storage through the server must wait for any open transactions to be completed. This can create a serious problem due to the continuous nature of video data. One solution to this problem has been to provide local storage in the client stations; however, this means that each client station must have its own hard disk, thereby adding cost and complexity to the system.
The present invention eliminates the need for a costly dedicated server and high performance network connection in audio/video media delivery applications. Instead of client stations requesting material from a server and waiting for the data to be delivered across the network from the storage device(s) via the server, each client station is locally connected to the storage device(s). Access is arbitrated locally over a relatively low performance (and consequently lower cost) network without stealing bandwidth from the storage interface.